In recent years, information processing instruments such as personal computers, mobile phones and PDAs (personal digital assistants) have been required to show a high processing speed in addition to be compact and lightweight. However, as the processing speed rises, there arise various problems including wire-attributable delays and EMIs (electromagnetic interferences).
Proposed techniques for avoiding wire-attributable delays and EMIs include the use of an optical wire or a line waveguide (U.S. Pat. No. 5,357,122).
Optical wires provide advantages including high speed transmission capabilities and being intrinsically free from electromagnetic inductions. However, in the above-mentioned technique using a line waveguide, optical wires having a thickness between several microns and tens of several microns are used and the wiring pattern is fixed. Therefore, the use of such a line waveguide is accompanied by a number of problems including the need of using a large number of optical switches, the difficulty of aligning optical axes, the need of micro-processing the optical waveguide, the use of a large number of parts and the difficulty of preparation if an enhanced degree of freedom for wiring and alteration of an optical circuit is to be desired.
U.S. Pat. No. 5,191,219, on the other hand, discloses an information processing apparatus comprising means for forming a planar optical waveguide which extends in two dimensions and serves as a shared medium, a plurality of light-emitting means and a plurality of light-detecting means extending in a two-dimensional arrangement over the planar optical waveguide for broadcasting light signals and abstracting light signals, respectively, into and from the planar optical waveguide, and a plurality of subsystems including input and output ports for processing the light signals in the shared medium, the light-detecting means being coupled to input ports and the light-emitting means being coupled to output ports of the subsystems.
However, the information processing apparatus disclosed in the above U.S. patent document is not satisfactory in terms of the degree of freedom for optical wiring.